Hereditary Tyrosinemia Type 1


What is Hereditary Tyrosinemia Type 1

Hereditary tyrosinemia type 1 is a rare genetic disorder characterized by the lack of the enzyme required to break down the amino acid tyrosine. This enzyme is called fumarylacetoacetate hydrolase (FAH). The resulting inability to break down tyrosine leads to abnormal accumulation in the liver, kidneys, and central nervous system. This can result in severe liver disease.

How common is Hereditary Tyrosinemia type 1

Hereditary tyrosinemia type 1 (HT-1) is a rare condition affecting approximately 1 in 110,000 births worldwide. It is usually recognized during newborn screening or during the first 3 months of life.

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What are the symptoms of Hereditary Tyrosinemia type 1

Symptoms can vary greatly from person to person in hereditary tyrosinemia type 1. The acute form of the disease is more common and present at birth or in the first months of life. Infants may exhibit rapid onset of symptoms typically starting with failure to gain weight and grow at the expected rate, known as failure to thrive. Additional symptoms may include fever, diarrhea, bloody stools (melena), and vomiting.

Eventually, patients may experience developmental delays, enlarged liver/spleen, and life-threatening liver failure. Additionally, many infants with hereditary tyrosinemia type 1 develop kidney dysfunction known as Fanconi syndrome. This condition leads to softening of the bone structure and overall weakness.

The chronic form of hereditary tyrosinemia type 1 occurs less frequently, with symptoms slower to appear and less severe. Onset is typically after 6 months of age, and the first symptom is often failure to thrive.

How is it diagnosed

A diagnosis of hereditary tyrosinemia type 1 is made based upon a thorough clinical evaluation, a detailed patient history, and a variety of specialized tests including molecular genetic tests. A diagnosis is likely if tyrosine metabolites and succinylacetone are detected in the urine. Genetic testing is available to identify mutations in the FAH gene for confirmation of diagnosis.

Note: All states include tyrosinemia in their newborn screenings, but some patients may not have elevated tyrosine levels in the first few days of life. This may cause them to test negative initially and have the diagnosis made after symptoms appear.


Hereditary Tyrosinemia type 1

The following specialty medications are available at Accredo, a specialty pharmacy for Hereditary Tyrosinemia type 1.

Medication Manufacturer
Nitisinone (Generic Orfadin) Multiple manufacturers
Nityr™ (nitisinone) tablets Cycle Pharmaceuticals

Financial Guidance

Life-saving specialty medication can be expensive. Learn how the Accredo teams help individuals find ways to afford the medication they need to survive in this video.

Find Support

There are many organizations that support research and advocacy for Hereditary Tyrosinemia Type 1. See below for a few of those organizations.

Support Organizations

Government Organizations

Meet the Team

Accredo’s Hereditary Tyrosinemia Type 1 team is dedicated to serving you and we understand the complexity of your condition. Our specialty-trained clinicians are available 24 hours a day, seven days a week, to answer any questions.

Why We Do It

Accredo supports patients with chronic and complex conditions and helps them live their best life. Watch our video to learn why we do what we do for our patients.

Why We Do It video transcript

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